Voltage selection and indication



Feb. 26, 1957 .1. L. FLANAGAN VOLTAGE SELECTION AND INDICATION Filed Deo. 6. 1955 N m M N A E A vr A f. L w M A l Tlg A Y A @W f Qn S0( S a@ A@ L A Nm. A MN NW QM, T A mv.. A A 52 v Lv NN) \\N Nwe k /Nnn @L -L LU i? Aj4 O. w w W Nm \W vk A 1 A A o NA .wv

r' 2,783,457 Patented Feb. 26, 1957 VOLTAGE SELECTIN AND INDICATION James L. Flanagan, Cambridge, Mass., assignor to the United States .of America as represented by the Secretary of the Air Force Application December` 6, 1955, Serial No. 551,477

Claims. (Cl. 340-248) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without payment to me of any royalty thereon.

This invention relates to voltage selection and indication, and more particularly to circuitry for selecting and indicating the maximum voltage of an arbitrary set of voltages.

A maximum amplitude selector of this type might be utilized in a speech compression system in the following manner. The said selector is used with an automatic spectrum analyzer for audio signals. The said selector is used to indicate the spectral maximum of certain audio signals by monitoring the outputs of a frequency analyzing device. The frequency analyzer yields output voltages that are proportional to the amplitudes of the frequency components of a given complex audio signal, and the maximum amplitude selector is used to indicate the frequency component having the maximum amplitude.

A further utilization of the maximum amplitude selector would be to categorize continuous speech into standard phonemes by cross-correlation of amplitude spectra. This is achieved by feeding speech to a set of audio analyzing filters. The short-time amplitude spectrum produced by the filter set is cross-correlated with standard formant patterns preset in a storage device, as illustrated more fully in my patent application No. 551,478 filed on even date herewith. The maximum amplitude selector picks the standard pattern affording the maximum correlation.

In the embodiment of the invention herein specifically illustrated and described, the apparatus provides a succession of visual indications of the maximum voltage of successively presented sets of unknown D. C. voltages, the visual indication in each instance being the illumination, or glow provided by a gas-discharge type of electronic tube. The voltage selected as the maximum of each successive set is indicated by the position of the gaseous glow in relation to an index element associated with a multicathode glow tube of the character indicated.

Still further objects and advantages of the invention will be appa-rent in the following description and the claims :considered together with the accompanying drawing shows a schematic wiring diagram embodying the invention.

Referring to the drawing more in detail, Fig. l shows a maximum voltage amplitude selector in which tube 1 is a ten-cathode, glow transfer tube, actuated by switching means including triode vacuum tubes 2 and 3. The anode 4 of tube 1 is loaded by series resistor 5 connected to the positive side of the plate voltage, the anode 6 of tube 2 is connected in parallel with the anode 4 of tube 1, tube 2 is provided with cathode resistor 7 and by-pass capacitor 8, the grid 9 of tube 2 is connected to ground through resistor 10 and 11, tube 2 is coupled through resistor 10 and capacitor 12 to tube 3, whose anode 13 is loaded by series resistor 14, connected to the positive side of the plate voltage, the cathode of tube 3 is provided with resistor 15 and by-pass capacitor 16, the grid 17 of tube 3 is grounded through resistors 18 and 19, tube 3 is driven from a square wave source and is coupled thereto by resistor 18 and capacitor 20.

The ten-cathode, glow transfer tube 1, has each of its respective cathodes 21 through 30 connected through their respective resistors 31 through 40 to the respective outputs of the D. C. amplifiers 41 through 50, the D. C. amplifiers 41 through 50 are fed from an amplitude normalizing network consisting of series of input resistors 51 through 60, aided by additional input resistors 61 through which compute the mean value of theinput signals and feed the resultant to the D. C. amplier 71, having a gain equal to -1, the output of the D. C. amplifier 71 is fed to resistors 72 through 81.

In the illustrated method of applying the invention, successive sets of unknown D. C. voltages are fed into input lines carrying resistors 61-70. The said voltages are then fed into the above-described normalizing network. The resulting normalized voltages are amplified by D. C. amplifiers 41-50. The normalized and amplified voltages are next presented to cathodes 21-30 of tube 1 by way of resistors 31-40. A glow i-s initiated at that particular one of Lsaid cathodes of tube 1 which at the moment is being supplied with the maximum voltage. Assuming the voltage supply to plate 4 to be pulsed (by way of tube 2) at 60 C. P. S. in order to ignite and extinguish tube 1 at the indicated recycling rate, there will be a corresponding pattern of successive identifications of the input circuits whose maximum voltages are thus successively presented.

A simplified ldiagram of a circuit arrangement for making the selection of the maximum voltage is shown in Fig. l. The `ten-cathode, glow transfer tube 1 (which may be Ericsson type GSlOC or its equivalent) has each of its cathodes 21 through 30 connected through resistors 31 through 40 to the output of D. C. amplifiers 41 through 50. The guide electrodes in the tube are left disconencted hence the glow can exist only at a cathode. The cathode voltages are depressed (i. e., made negative) proportional to positive voltages appearing at the D. C. amplifier inputs. The plate supply voltage of the glow tube 1 is effectively switched on and oi by the triode .switch tube 2 to allow the tube 1 to ignite and extinguish alternately. The glow is initiated at the cathode whose potential has been depressed the greatest amount each time the tube is enabled to ignite. Switching of the plate supply is accomplished by vacuum triodes 2 and 3, anode 6 of triode 2 being [connected in parallel with the anode 4 of tube 1. Triode 2 is alternately driven beyond cut-off and into heavy conduction by triode 3 which receives its input from a square wave source, supplied to terminal 81. Selection of the voltage having the maximum value is made therefore at the enabling-disabling rate.

The D. C. amplifiers 41 through 50 are fed from a resistive normalizing network consisting of resistors 51 through 60, 61 through 70, a D. C. amplifier 71 with unity gain which reverses polarity, and resistors 72 through 81. rl`he network computes the mean value of the set of input voltages and subtracts this mean value from each member of the input set. It provides one half of this difference `at each corresponding out. For example, if ek is the voltage input for the kth channel of a group of channels of total number, N, then the normalized output for the kth channel is:

Presently N=l0, but glow tubes having twelve cathodes are available. Normalization of the voltage amplitudes 3 allows the mean level of the Set of input voltages to vary over a range greater than 30 `db without influencing the selection of the maximum voltage. To reliably position the glow in tube l at a given cathode, its potential must be approximately 40 volts more negative than the cathode with the next lowest potential. This value is relatively large but at the inputs of theD. C. amplifiers 41 through Si?, this value is divided by the gain of thek amplifiers.

The device is primarily a visual indicator, but an electrical output can be obtained across the resistors in each cathode of the glow tube 1. Differential amplifiers connected `across the cathode resistors 31 through 40 can be used to obtain electrical output when a particular cathode conducts. The differential amplifiers can be used to actuate additional equipment for indicating or for antomatically measuring or utilizing maximum voltage.

What is claimed is:

l. A multi-channel maximum voltage amplitude selector comprising a plurality of parallel circuits each adapted to receive one of a series of variable input voltages, means for normalizing and amplifying each of said input voltages prior to delivery to said parallel circuits, an electronic discharge indicator device having a'plurality of cathodes distributed among said parallel circuit-s, means for delivering to the said device the output voltages from each of said parallel circuits, and means including a single energy supply element for producing luminous electron emission from one of said cathodes whenever its associated one of said parallel circuits is operating at a voltage gradient greater than that of any other of said parallel circuits.

2. A multi-channel maximum amplitude voltage selector as defined in claim l, wherein the said normalizing means includes a resistor network and polarity reversing means.

3. A multi-channel maximum voltage amplitude lselector las deiined in claim 2, wherein the said polarity reversing means is comprised of a unity-gain direct current ampliiier embracing all of said channels.

4. A multi-channel maximum-voltage amplitude selector as defined in claim 2 and further including a D. C. amplilier adapted to receive the output voltages of the said normalizing means. v

5. A multi-channel maximum voltage amplitude selector as defined in claim 4, wherein the said electronic discharge indicator consists of a multi-.cathode glow transfer tube and wherein each of said parallel circuits includes a resistor controlling energy tlow to the respective cathodes.

6'. A multi-channel maximum voltage amplitude selector as defined in claim 5, wherein the said means for causing the said device to indicate the presence of the maximum amplitude voltage is comprised of sai'd multi-cathode glow tube, and means for controlling intermittent energization thereof.

7. A multi-channel maximum voltage amplitude selector as deiined in claim 6, wherein said energization controlling means includes electronic pulsing means controlling current flow to said multi-cathode glow tube.

8. A multi-channel maximum voltage amplitude selector adapted to receive direct current input voltages the maximum of which is to be selected, comprising a multichannel resistive network, unity-gain amplifying and inverting means common to all channels of said network for normalizing the voltage amplitudes 4applied to said network, a plurality of Idirect current amplifiers receiving the output of said network, a multi-cathode glow transfer tube having each of its cathodes connected through a resistor to the output of the said direct current ampliers, a source of direct current anode supply voltage connected to the anode of said multidcathode glow transfer tube, and means for switching the said direct current anode supply voltage on and olf.

9. A multi-channel maximum voltage amplitude selector as defined in claim 8, wherein the said switching means is comprised of an amplifier connected in parallel with the anode of the multi-cathode glow transfer tube and driven from a square wave source.

10. A multi-channel voltage amplitude selector for selecting and identifying the single maximum amplitude voltage of each of a set of successively presented input voltages, said selector comprising normalizing and amplifying-means eective successively upon each of said sets of input voltages, voltage-sensitive means for receiving each of said normalized and amplified voltages, and means for indicating the particular input of the set whose maximum voltage is being determined at any given instant. v

References Cited in the file of this patent UNITED STATES PATENTS 1,961,574 Senauke lune 5, 1934 2,486,890 Stanmyre Nov. l, 1949 2,592,342 Rycltm'an Apr. 8, 1952 2,652,555 Smith Sept. l, 1953 2,675,538 Malthaner et al Apr. 13, 1954 

